This third volume of the series on coastal engineering concentrates on a single specialized topic: breakwater design. The subdivisions into four categories found in the previous two volumes is not found here; all of this volume relates to harbors in some way. Of course, some information presented here can be used elsewhere. For example, knowledge of wave impact forces, important for the design of monolithic breakwaters, can also be handy when designing offshore structures. A more direct tie can be made between the design methods used for breakwaters and those needed for coastal defense works volume I, chapter 30.
f5N Coastal Engineering Volume 111Breakwater Design January 1986 Edited by W W Massie, P E l1,}~,( TH Delft Delft University of Technology Department of Civil Engineering Hydraulic and Geotechnical EngineeringGroup 229 COASTAL ENGINEERING Volume 111 - Breakwater Design edited by W.w Massie, P.E Coastal Engineering Group Department of Civil Engineering Delft University of Technology DELFT The Netherlands First edi t i on Nov , 1976 Revised printing Dec 1979 Reprinted ~ith some corrections, Winter 1985/86 T\I- tudent -f5fJ - 03 1604019 pr ice f 7,25 i TABLE OF CONTENTS - VOLUME 111 BREAKWATER DESIGN Page Introduction 1.1 Scope 1.2 Contributors 1.3 References 1.4 Miscellaneous Remarks 1.5 Additional Remarks for Second Edition General Considerations 2.1 Purposes 2.2 General Design Information 2.3 Sources of Design Data 2.4 Performance Requirements 2.5 Review 1 1 3 Types of Breakwaters 3.1 Introduction 3.2 Comparison of Types 3.3 Conclusions 10 Rubble Mound Breakwaters 4.1 Definition 4.2 Two Distinct Types 4.3 Basic Construction Principles 20 21 Wave Run-up and Overtoppin~ 5.1 lntroduction 5.2 Run-up Determination 5.3 Run-up in Relation to Breakwater Design 5.4 Conclusions about Run-up 5.5 Wave Overtopping 5.6 Wave Transmission 22 22 22 24 25 25 26 Construction Materials 6.1 Necessary Properties 6.2 Desirable Properties 6.3 Characterizing Coefficients for Armor Units 6.4 Armor Unit Types 6.5 Armor Selection 6.6 Methods to increase Stability 28 6.7 Concludin~ Re~ark Armor Computations 7.1 History 7.2 Theoretical Background 7.3 T~e Hudson Formula 7.4 Special Applications 7.5 Sensitivity of Hudson Formula 10 10 19 20 20 28 28 29 30 35 36 37 37 37 40 42 43 i TABLE OF CONTENTS - VOLUME 111 BREAKWATER DESIGN Page Introduction 1.1 Scope 1.2 Contributors 1.3 References 1.4 Miscellaneous Remarks 1.5 Additional Remarks for Second Edition General Considerations 2.1 Purposes 2.2 General Design Information 2.3 Sources of Design Data 2.4 Performance Requirements 2.5 Review 1 1 3 Types of Breakwaters 3.1 Introduction 3.2 Comparison of Types 3.3 Conclusions 10 Rubble Mound Breakwaters 4.1 Definition 4.2 Two Distinct Types 4.3 Basic Construction Principles 20 21 Wave Run-up and Overtoppin~ 5.1 lntroduction 5.2 Run-up Determination 5.3 Run-up in Relation to Breakwater Design 5.4 Conclusions about Run-up 5.5 Wave Overtopping 5.6 Wave Transmission 22 22 22 24 25 25 26 Construction Materials 6.1 Necessary Properties 6.2 Desirable Properties 6.3 Characterizing Coefficients for Armor Units 6.4 Armor Unit Types 6.5 Armor Selection 6.6 Methods to increase Stability 28 6.7 Concludin~ Re~ark Armor Computations 7.1 History 7.2 Theoretical Background 7.3 T~e Hudson Formula 7.4 Special Applications 7.5 Sensitivity of Hudson Formula 10 10 19 20 20 28 28 29 30 35 36 37 37 37 40 42 43 ii 7.6 7.7 7.8 7.9 Choice of Armor Units Layer Extent and Thickness Crest Width Review 44 45 47 47 The Core 8.1 Function 8.2 Materials 8.3 Construction Methods 48 48 48 49 Filter and Toe Constructions 9.1 Description and Functions 9.2 The Physical Phenomena Involved 9.3 Design Criteria for Filters 9.4 Design Criteria for Toes 9.5 Filter Layer Constructions 9.6 Toe Constructions 9.7 Other Foundation Problems 50 50 50 51 51 51 54 57 10 Rubble Mound Breakwater Construction 10.1 Introduction 10.2 Construction Methods 10.3 Specific Constructional Aspects 10.4 Special Construction Problems 10.5 Review 58 58 58 60 62 63 11 Optimum Design 11.1 Introduction 11.2 Parameters and their Interrelationships 11.3 Given Data 11.4 Preliminary Calculations 11.5 Cost of Quarry Stone Breakwater 11.6 Damage to the Breakwater 64 64 64 65 68 11.7 Optimization of Quarry Stone Breakwater 11.8 Additional Remarks 72 78 81 84 12 Example of Rubble Mound Breakwater 86 13 Monolithic Breakwaters 13.1 Definition 13.2 General Features 87 87 87 14 Construction Materials 14.1 Introduction 14.2 Environmental Di fferences 14.3 Consequences for Materials 91 91 91 91 formation As an alternative, wave statistics can sometimes be derived from other information as explained in chapter 12 of volume I Storm surge data is also of ten recorded at coastal stations by the weather service Theoretical prediction is sometimes possible when measurements are lacking; an approach to the problem is outlined in volume I chapter Information about the soil conditions at a site is often more difficult to find Possibly local public works agencies or dredging contractors who have worked in the area may be able to provide some information Even so, a detailed geotechnical survey of the area will very of ten be required, especially if a large or special project is involved Any information concerning special design specifications, such as recreational requirements will be provided by the authoritv initiating the project Data from which an impression of coastal morphological changes can be obtained may be held by public works agencies or may be derived from comparison of present and past navigation charts Libraries often have map collections which can be used for these comparison studies 2.4 Performance Requirements Several factors which can influence our choice of breakwater type have already been mentioned These have been grouped under purpose and under design information in earlier sections of this chapter In this section other factors affecting the choice of design type will be considered A catalog of types of breakwaters with their advantages and disadvantages will be presented in chapter In contrast to dikes, the performance requirements for breakwaters are usually much less stringent For example, a breakwater may be needed only temporarily such as those used to establish the beachheads in World War 11 On the other hand; a permanent structure may be desirable, but this structure need only be effective intermittently One can conceive of a ferry harbor entrance which only need be protected from wave action when the ferry is moving in or out Available construction and maintenance methods can also result in modified designs If, for example, navigational aids and the breakwater itself must be repaired quickly, then a higher crest elevation may be dictated by the need to move equipment along the dam during severe weather Indeed, for some purposes, a breakwater need not be much higher than the still water level, while for others it must be nearly as high as a dike If quay facilities are to be provided on the inner side of the breakwater, special foundations will be required to withstand the additional loads from cargo handling and to limit settlement Another contrast with dike is that a breakwater need not always be impermeable Some types of breakwaters such as air bubble curtains or floating breakwaters little to restrict currents iv LIST OF TABLES Table number Title 1.1 Contributing Staff 7.1 Comparison of armor units 45 67 11.6 Storm data Costs of Materials in place Wave shoaling Initial cost estimate - stone breakwater Cost as function of Wave height for stone breakwater Breakwater damage computations 11 Cost Summary 16.1 Response to schematized forces Breakwater sliding parameters Sliding computation 104 109 123 125 19.6 19.7 19.8 Storm data Costs of Materials in Place Wave computations Statistical calculation for Hd 8.0 m Element quantities Wave force Computations Additional breakwater sliding parameters Optimization computations 20.1 Overview of breakwater types 154 11.1 11.2 11.3 11.4 11.5 16.2 16.3 19.1 19.2 19.3 19.4 19.5 Page 68 71 76 78 80 81 82 113 126 127 133 135 133 143 v LIST OF FIGURES Page Figure number Title 2.1 2.2 2.3 2.4 Plymouth Harbor, U.S.A Columbia River entrance Influence of cross current on ship Current pattern at Europoort entrance 3.1 3.2 3.3 Air bubble curtain Composite breakwater Resonant breakwater 10 4.1 4.2 Overtopping breakwater Non overtopping breakwater 20 21 5.1 5.2 5.3 Wave run-up Run-up - steepness curves Wave transmission for submerged breakwaters 23 24 27 6.1 6.2 6.3 6.4 6.5 6.6 6.7 Akmon armor unit Cob Concrete cube Modified cube forms Dolos Tetrapod Tribar 30 7.1 7.2 7.4 Force diagram for single armor unit Limits of Armor Equations Equilibrium along contour Comparison of armor units 9.1 9.2 9.3 9.4 9.5 9.6 Pressures within breakwater Woven fabric mattress Woven fabric mattress with concrete block Conventional excavated toe construction Alternative toe construction Toe construction without excavation 50 52 53 10.1 Breakwater constructed with core protection 62 11.1 11.2 Storm wave and water level data Wave data at site 66 70 11.3 11.4 Sketch design of stone breakwater Damage relationship for rough quarry stone Cost curves for stone breakwater 75 7.3 11.5 5 11 16 31 31 32 32 34 35 37 40 43 45 55 56 56 78A 83 30 Details about a variety of armor units, listed in alphabetical order, are given in the following section Agema (1972) and Hudson (1974) also give summaries of available block forms Unless otherwise specified, damage coefficient values are given for a double layer of randomly placed armor units subjected to non-breaking wa yes in the ma in body of the breakwater x "Percent damage" refers to the percentage of armor units in the area exposèd to attack which are displaced so far that they no longer fulfill their function as armor This rather arbitrary damage measurement is chosen for its ease of measurement (via counting) and utility in optimum design procedures 6.4 Armor Unit Types a Akmon An anvil shaped plain concrete block - the name comes from the Greek for anvil - developed in 1962 by the Delft Hydraulics Laboratory A photo of such a block is shown in figure 6.1 Because of their high KD value, a massive monolithic crest is suggested The density of the blocks is the same as that for concrete The damage coefficient has been found to vary according to the allowable damage as follows: Damage KD (%) 4.8 1l 12 ;;;17 Further, slopes of up to 1:1.33 are possible The porosity, n, is 55 to 60%, and the layer coefficient, K6 is about 1.00 The data presented above are based upon only a limited number of model tests.*· Reference: Paape and Walther (1962) Figure 6.1 AKMON ARM OR UN IT ~ See chapter and Share Protection Manual • ~ See also section 6.7 1 INTRODUCTION W.W Massie 1.1 Scope This third volume of the series on coastal engineering concentrates on a single specialized topic: breakwater design The subdivisions into four categories found in the previous two volumes is not found here; all of this volume relates to harbors in some way Of course, some information presented here can be used elsewhere For example, knowledge of wave impact forces, important for the design of monolithic breakwaters, can also be handy when designing offshore structures A more direct tie can be made between the design methods used for breakwaters and those needed for coastal defense works - volume I, chapter 30 1.2 Contributors The primary authors are listed at the beginning of each chapter; final editing and coordination was done by W.W Massie layout by P Lapidaire Table 1.1 lists the staff members of the Coastal Engineering Group who contributed to this volume 1.3 References One general reference is so handy for breakwater design that it is not repeatedly mentioned This book is the Share Protection Manual published in 1973 by the U.S Army Coastal Engineering Research Center Information presented well there will not be duplicated here; these notes complement rather than replace the Shore Pratection Manual 1.4 Miscellaneous Remarks As in previous volumes, the spelling used is American rather than English A list of Dutch, Frenëh and German translations of the more important technical words is available The notation used is kept as consistent as possible with previous volumes and with internationally accepted practice A symbol table is included in this volume, even though most symbols are defined in each chapter as they appear Literature is listed in the text by author and year; a more complete listing is included separately in the book More general introductory material may be found in chapter of volume I of these notes 162 W.W SYMBOLS AND NOTATION Massie The symbols used in this set notes are listed in the table International standards of notation have been used where available except for occasional uses in which direct conflict of meaning would result Certain symbols have more than one meaning, however this is only allowed when the context of a symbol's use is sufficient to define its meaning explicitly For example, T is used to denote both wave period and temperature In the table a meaning given in capital letters indicates an international standard The meaning of symbols used for dimensions and units are also listed toward the end of the table Roman Letters Symbol Defi nition A a a13 CROSS SECTIONAL AREA coefficient acceleration 7.02 16.01 13 bouyant force coefficient breakwater width 16 J.8 7.08 16.40 b b C Cz number of armor uni ts per unit surface area contact force spring constant spri ng constant spri-ng constant d block "diameter" e BASE OF NATURAL LOGS Fx Fz force in x di recti on force in z direction Cx c~ Cx Equation 7.22 16.11 Hi.02 16.03 16.02 7.01 16.03 16.02 dimensions Uni ts L2 m2 LT-2 m/s2 MLT-2 N L-2 11m2 MLT-2 r~L2T-2 MT-2 MT-2 N Nm/rad Nim Nim L m MLT-2 MLT-2 N N 163 Symbol Definition Fw wave force FF f f friction force frict ion force failure in P(f) ACCELERAT10N OF GRAV1TY H WAVE HE1GHT design wave height incident wave height significant wave height significant wave height at deep water transmitted wave height maximum progressive wave component wave height at deep water unknown wave height WATERDEPTH depth to toe of armor waterlevel total height of breakwa ter Hd H·1 Hs i9 Hs i9 Ht Hx H~ H h h' hot dimensions Units MLT-2 MLT-2 MLT-2 N N N LT-2 m/s2 7.01 19.02 15.01 11.03 L L L L m m m m 11.04 L m 5.04 L m fig 5.02 7.19 tab.11.3 11.05 tab.l1.1 19.07 L L L L L L m m m m m m ML2 ML2 ML2 ML2 kgm2/rad kgm2/rad kgm2/rad kgm2/rad Equation 16.17 16.21 7.04 19.58 1wy 1sy virtual inertia virtual inertia virtual inertia subscript index 16.04 16.04 16.04 16.04 J constant 19.40 K k constant WAVE NUMBER 2n/À 19.43 15.01 L L Length of impacting mass 15.03 L m M fvly m m' mass moment number of layer of armor units number of uni ts across crest breakwater mass virtual soil mass virtual water mass 16.05 16.04 7.21 7.23 16.02 16.01 16.03 M ML2T-2 kg Nm M M M kg kg kg r,lL T-2 N 11:) mB ms ~ N N normal force number of waves 7.03 tab.19.3 -1 l/m 164 Symbol Definition N' n dynamie normal force s1ope poros ity 16.18 5.01 P( ) probability 19.02 P pressure R R r Equation dimensions Units MLT-2 N 15.01 ML-1T-2 N/m2 run up hydraul ie radius s1ope roughness 5.01 15.05 5.01 L L L m m m T t t PERrOD (wave) TIME Layer thiekness 5.01 15.01 7.21 T T L s s;hr m u COMPONENT VELOCITY IN X DIRECTION LT-1 mis V v TOTAL VELOCITY COMPONENT VELOCITY IN Y DIRECTION 15.02 16.24 LT-1 LT-1 mis mis W Wsub w breakwater weight bloek weight COMPONENT VELOCITY IN Z DIRECTION 16.18 7.03 MLT-2 MLT-2 LT-1 N N mis X x x COORDINATE DIRECTION COORDINATE DIRECTION horizontal displacement 16.01 16.32 L L L m m m Y y COORDINATE DIRECTION COORDINATE DIRECTION 16.01 L L m m Z z ze COORDINATE DIRECTION COORDINATE DIRECTION erest elevation above SWL 15.01 5.02 L L L m m m of ( 165 GREEK LETTERS Symbol Definition Equation a breakwater slope 5.01 rad foreshore s1ope 5.01 rad y breaker index /::, RELATIVE DENSITY 7.11 15.03 dynamic pressure coefficient 16.20 e slope angle 7.03 À WAVE LENGTH fig.5.2 u friction coefficient TI 3.1415926536 P Pa PB Ps lJENSITYOF density of density of density of